Methods and Apparatus for Treating Spinal Stenosis

ABSTRACT

This invention relates generally to spine surgery and, in particular, to methods and apparatus for treating spinal stenosis.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/540,318, filed Sep. 28, 2006, now pending, which claims the benefitof the filing date under 35 USC 119(e) of provisional applicationentitled “Methods and Apparatus for Treating Spinal Stenosis,” Ser. No.60/722,065, filed Sep. 28, 2005, the entire contents of which is fullyincorporated herein by reference.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates generally to spine surgery and, in particular, tomethods and apparatus for treating spinal stenosis.

II. Discussion of the Prior Art

Spinal stenosis is a narrowing of spaces in the spine which results inpressure on the spinal cord and/or nerve roots. This disorder usuallyinvolves the narrowing of one or more of the following: (1) the canal inthe center of the vertebral column through which the spinal cord andnerve roots run, (2) the canals at the base or roots of nerves branchingout from the spinal cord, or (3) the openings between vertebrae throughwhich nerves leave the spine and go to other parts of the body. Pressureon the spinal cord and/or exiting nerve roots may give rise to pain ornumbness in the legs and/or arms depending on the location within thespine (e.g. cervical, thoracic, lumbar regions). While spinal stenosisgenerally afflicts those of advanced age, younger patients may suffer aswell.

A variety of treatments have been undertaken to alleviate or minimizethe effects of spinal stenosis. One such technique is a laminectomy,which involves removing the lamina portion from the pathologic region.By removing the lamina, this procedure enlarges the spinal canal andthus relieves the pressure on the spinal chord and/or compressed nerves.While generally effective, some consider lamimectomy disadvantageous inthat, as with any procedure involving bone removal, the resulting regionof the spine may be further compromised from a mechanical standpoint.Moreover, elderly patients frequently have co-morbidities that increasethe likelihood of complications, such as increased back pain, infection,and prolonged recovery.

Still other efforts at treating spinal stenosis involve placing spacerdevices within the inter-spinous space to indirectly decompress thestenotic condition. These systems are characterized by being secured atthe superior and inferior spinous processes. Having both ends of thespacer device coupled to the respective spinous processesdisadvantageously limits both flexion and extension of the spine at thatlocation, when it is believed that limiting extension is the key torelieving spinal stenosis. Moreover, the prior art inter-spinous spacersare typically constructed from materials (e.g. metal) with propertiessubstantially different than that of the spinous processes themselves,which raises questions of whether the spinous processes will remodelaround the spacer and thereby lose their ability to distract and therebyalleviate spinal stenosis.

The present invention is directed at overcoming, or at least improvingupon, the disadvantages of the prior art.

SUMMARY OF THE INVENTION

The present invention is directed at treating spinal stenosis involvingan inter-spinous spacer dimensioned to distract a stenotic inter-spinousspace and further characterized as being affixed to only one of the twoadjacent spinous processes to prevent spinal extension and allow spinalflexion. The inter-spinous spacer of the present invention may be usedin the cervical, thoracic and/or lumbar spine. Although shown anddescribed throughout this disclosure with the inter-spinous spaceraffixed to the superior spinous process, it will be appreciated that theinter-spinous spacer of the present invention may also be affixed to theinferior spinous process without departing from the scope of theinvention. Various mechanisms may be used to affix the inter-spinousspacer of the present invention to the given spinous process, includingbut not limited to one or more tethers (e.g. wire, cable, suture,allograft tissue, or other single or multi-filament members), one ormore screws and/or any of a variety of clamping mechanisms.

According to an important aspect of the present invention, theinter-spinous spacer of the present invention is designed to fuse to thespinous process to which it is affixed over time, resulting in what iscalled “hemi-fusion” in that the spacer will be fused to only onespinous process. This is facilitated by abrading the surface of thespinous process (to preferably cause bleeding) where it will mate withthe inter-spinous spacer of the present invention. This junction willfuse over time based, in part, on the fusion-enabling design and/ormaterial of the inter-spinous spacer of the present invention. Morespecifically, the inter-spinous spacer of the present invention may beconstructed from bone (e.g. allograft) material, which is readily knownto enable fusion upon implantation. The inter-spinous spacer may also beconstructed from non-bone materials (e.g. polyaryletheretherketone(PEEK) and/or polaryletherketoneketone (PEKK)) which are physicallydesigned to promote fusion. This is accomplished, by way of example, byproviding an interior lumen within the inter-spinous spacer which isdimensioned to receive fusion-inducing materials and which is incommunication with the abraded surface of the given spinous process.Such fusion-promoting materials may include, but are not necessarilylimited to BMP, demineralized bone matrix, allograft cancellous bone,autograft bone, hydroxy appetite, coral and/or other highly poroussubstances.

The present invention overcomes the drawbacks of the prior art bytreating spinal stenosis while allowing spinal flexion with an implantconstructed from materials with properties substantially closer to theproperties of the spinous processes themselves than prior art devices.This advantageously minimizes the risk of the spinous processesremodeling around the inter-spinous spacer of the present invention,which advantageously prevents and/or minimizes the risk of a loss ofdistraction that may otherwise occur.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a perspective view of an inter-spinous spacer according to afirst embodiment of the present invention in use affixed to a superiorspinous process of a human spine;

FIG. 2 is a perspective view of the inter-spinous spacer of the presentinvention shown in FIG. 1;

FIG. 3 is a side view of the inter-spinous spacer of the presentinvention as shown in FIG. 1;

FIG. 4 is a front view of the inter-spinous spacer of the presentinvention as shown in FIG. 1;

FIG. 5 is a top view of the inter-spinous spacer according to thepresent invention as shown in FIG. 1;

FIG. 6 is a cross-sectional view of the inter-spinous spacer of thepresent invention as taken through lines A-A of FIG. 5;

FIG. 7 is a perspective view illustrating the inter-spinous spacer shownin FIG. 1 with fusion-promoting materials disposed within an inner lumenaccording to one aspect of the present invention;

FIG. 8 is a perspective view of an inter-spinous spacer according to asecond embodiment of the present;

FIG. 9 is a side view of the inter-spinous spacer according to thepresent invention as shown in FIG. 8;

FIG. 10 is an end view of the inter-spinous spacer according to thepresent in invention as shown in FIGS. 8-9;

FIG. 11 is a perspective view of an inter-spinous spacer according to athird embodiment of the present invention in use affixed to a superiorspinous process of a human spine;

FIG. 12. is a frontal view of the inter-spinous spacer according to thepresent in invention as shown in FIG. 11, in place in between the twospinous processes;

FIG. 13. is a side view of the inter-spinous spacer according to thepresent in invention as shown in FIG. 11, in place in between the twospinous processes;

FIG. 14. is a side view of the inter-spinous spacer according to thepresent in invention as shown in FIG. 11, in place in between the twospinous processes with fusion inducing material packed inside;

FIG. 15 is a front view of the inter-spinous spacer according thepresent invention as shown in FIG. 11;

FIG. 16 is a top view of an inter-spinous spacer according the presentinvention as shown in FIG. 11;

FIG. 17 is a back side view of an inter-spinous spacer according thepresent invention as shown in FIG. 11;

FIG. 18 is bottom view of an inter-spinous spacer according the presentinvention as shown in FIG. 11;

FIG. 19 is a side view of an inter-spinous spacer according the presentinvention as shown in FIG. 11;

FIG. 20 is perspective view of an inter-spinous spacer according thepresent invention as shown in FIG. 11 including visualization markers;

FIGS. 21-23 illustrate an exemplary insertion tool in use with theinter-spinous spacer of FIG. 11, according to one embodiment of thepresent invention;

FIGS. 24-27 illustrate an exemplary sizer tool for use when implantingthe inter-spinous spacer as shown in FIG. 11; according one embodimentof the present invention;

FIGS. 28-29 illustrate an alternate attachment device for use with theinter-spinous spacer shown in FIG. 11 according to an alternateembodiment of the present invention;

FIG. 30 illustrates a posterior fluoroscopy view taken duringimplantation of the inter-spinous spacer of FIG. 11 demonstrating thealignment of markers (including the formation of a “T”) to aid inplacement; and

FIG. 31 illustrates a lateral fluoroscopy view taken during implantationof the inter-spinous spacer of FIG. 11 demonstrating the position ofmarkers (including the formation of a backwards “L”) to aid inplacement.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The spinal alignment system disclosed herein boasts avariety of inventive features and components that warrant patentprotection, both individually and in combination.

FIG. 1 illustrates a perspective view of a spinous process spacer 10 ofthe present invention in use between two spinous processes in a humanspine. The spacer assembly 10 includes a spacer 12, a primary spinousprocess tether 14, and two side tethers 15 (only one of which is shownin FIG. 1). The spacer 12, as illustrated in FIGS. 2-6, is generallycylindrical and includes a main chamber 16, a pair of insertion toolapertures 18, a fusion notch 20, and a pair of tether lumens 22. As willbe described in greater detail below, the spacer 12 is (according to apreferred embodiment) coupled to only the superior spinous process suchthat the spacer 12, with no coupling to the inferior spinous process.This is accomplished, but way of example only, by securing the primaryspinous process tether 14 to the superior spinous process (as a firststep of affixation), followed by passing one side tether 15 through eachof the tether lumens 22, in between the superior spinous process and theprimary spinous process tether 14, and finally tightening each sidetether 15 until the spacer 12 is generally transverse to thelongitudinal axis of the spine.

The spacer 12 may be of bone or non-bone construction. The boneembodiment involves manufacturing the spacer 12 from a suitableallograft, including but not limited to clavicle, rib, humerus, radius,ulna, metacarpal, phalanx, femur, tibia, fibula, or metatarsal bone. Thenon-bone embodiment involves manufacturing the spacer 12 from suitablenon-bone materials, including but not limited to polyaryletherketone(PEEK) and polyaryletherketoneketone (PEKK). In either event, the spacer12 is designed to fuse to the superior spinous process over time,resulting in what is called “hemi-fusion” in that the spacer 12 will befused to only one spinous process. This may be augmented by disposingany number of suitable fusion-inducing materials within the spacer 12,including but not limited to BMP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14 . . . n, demineralized bone matrix, allograft cancellous bone,autograft bone, hydroxy appetite, coral and/or other highly poroussubstance.

Although shown and described with regard to the superior spinousprocess, it will be appreciated that the spacer 12 may also be coupledto only the inferior spinous process without departing from the scope ofthe present invention. The spacer 12, once positioned, serves todistract the inter spinous process space, which advantageously restoresforaminal height in stenotic patients and may also indirectly decompressthe intervertebral space.

As depicted in FIGS. 2-3, the main chamber 16 extends through thelateral sides of the spacer 12. The main chamber 16 may be provided inany of a variety of suitable shapes in addition to the generallycylindrical shape shown, including but not limited to a generallyoblong, triangular, rectangular shape and/or combinations thereof. Themain chamber 16 may be dimensioned to receive fusion inducing materials32, as best illustrated in FIG. 8. Again, such fusion inducing materialsmay include, but are not necessarily limited to BMP1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14 . . . n, demineralized bone matrix, allograftcancellous bone, autograft bone, hydroxy appetite, coral and/or otherhighly porous substance. The fusion inducing materials may be packedinto main chamber 16 before and/or after fixing spacer 10 to the spinousprocess. The pair of insertion tool apertures 18 may be located oneither the posterior or anterior side of the spacer 12 and extend aportion of the way through the spacer 12. The fusion notch 20 includes aslot or indent to receive a portion of an upper spinous process or othervertebral feature to enhance fusion. The notch 20 may be locatedgenerally on the top surface towards the middle portion of the spacer12. The notch 20 helps center the spacer 12 relative to the superiorspinous process.

According to another embodiment, shown in FIGS. 9-11, the spacer 12 maybe provided with a second notch 21 opposite the fusion notch 20. Thesecond notch 21 is capable of resting on the inferior spinous processduring use, which may assist in maintaining the spacer 12 in a fullycentered position relative to the inferior spinous process. As bestshown in FIG. 9, the fusion notch 20 may be further provided with slots23 extending into the main chamber 16. When the spacer 12 is coupled tothe superior spinous process, these slots 23 will establish directcommunication between the fusion-inducing compounds provided within themain chamber 16 and the lower aspect of the superior spinous process,which advantageously augments the ability of the spacer 12 to fuse tothe superior spinous process (particularly if the spacer 12 isconstructed of non-bone materials).

As best shown in FIG. 6, the tether lumens 22 each extend at an anglethrough the top surface of the spacer 12 and into the main chamber 16.Each tether lumen 22 may be provided in any of a variety of suitableshapes in addition to the cylindrical shape shown, including but notlimited to oblong, triangular, rectangular and/or any combinationthereof. The tethers 14, 15 may comprise any number of suitablematerials and configurations, including but not limited to wire, cable,suture (permanent and/or bioresorbable), allograft tissue and/or othersingle or multi-filament member. Suture thread may include any number ofcomponents capable of attaching to a spinous process, including but notlimited to ordinary suture threads known to and used by those skilled inthe art of wound closure. Suture thread may be of any length necessaryto effectively fuse the spacer 12 to the particular spinous process.

The spacer 12 according to the present invention may be constructed ofallograft bone and formed in a generally cylindrical shape. The spacer12 of the present invention may be provided in any number of suitableshapes and sizes depending upon a particular patient and the shape andstrength characteristics given the variation from cadaver to cadaver.The spacer 12 may be dimensioned for use in the cervical and/or lumbarspine without departing from the scope of the present invention. Thespacer 12 may be dimensioned, by way of example only, having a lengthranging between 6-20 mm and a height ranging between 20-25 mm.

When constructed from allograft, the spacer 12 may be manufacturedaccording to the following exemplary method. A belt sander may first beused to reduce any high spots or imperfections to standardize the shapeof the bone. Cut the allograft bone to length using the band saw. Removethe cancellous material from the inner canal to create the main chamber16. Using calipers, measure the struts and create a size distribution ofspacers 12. Machine the insertion tool apertures 18. Set-up a standardvice for holding the implant across its width on the mill. Use a 3/32″ball end mill to create the insertion tool apertures 18 (same ascervical allograft implant). Insert the spacer 12 into the vice andtighten. Calculate the centerline of the 20 or 25 mm long spacer 12.Create the holes 2.26 mm away from each side of the centerline (4.52 mmhole to hole distance). Create a notch 22 for the spinous process.Set-up the cervical allograft holding fixture that uses the insertiontool apertures 18 and vice to hold the spacer 12 across its width on themill. Use a ¼″ flat end mill to create the notch 22. Calculate thecenterline of the 20 or 25 mm long spacer 12. Insert the spacer 12 ontothe fixture using the insertion tool apertures 18 and tighten the vice.This automatically verifies the correct sizing/spacing of the insertiontool apertures 18. Measure the spacer 12 height. Calculate the cut depthto create the desired spacer 12 size. Cut the flat on the spacer 12 tothe desired depth. Remeasure the spacer 12 to insure proper cut depth.Drill the angled lumens 22 in face of spacer 12. Remove the spacer 12from the cervical allograft fixture and tighten into the standard vice.Using a battery powered or corded drill with a 1/16″ drill bit, drillthrough the front face to the canal on both sides. Belt sand the face ifneeded to create a flat surface for the drill bit to engage the spacer12.

Turning now to FIG. 11 there is shown in perspective view an example ofa spacer 112 according to another embodiment of the present invention.Spacer 112 includes a posterior side 113, anterior side 114, lateralsides 115, a main chamber 116, and a fusion notch 120. Spacer 112 isfurther provided with a plurality of apertures including, but notnecessarily limited to, three pairs of insertion tool apertures 118 a,118 b, and 118 c, tether lumens 122, and fusion apertures 124.

FIGS. 12-14 depict spacer 112 in use in the inter spinous process spaceof a patient. Spacer 112 is designed to fit between a superior spinousprocess and an inferior spinous process and may be dimensioned in anynumber of suitable shapes and sizes to accomplish this. The spacer 112may be positioned in any of the cervical, thoracic, and/or lumbar spineand sizes may vary accordingly. When in position, a properly sizedspacer 112 distracts the inter spinous process space, restoring theforaminal height in stenotic patients and indirectly decompresses theintervertebral space. By way of example only, spacer 112 may bedimensioned having a length ranging between 6-20 mm and a height rangingbetween 20-25 mm.

Spacer 112 is preferably constructed of non-bone material. Suitablenon-bone materials may include, but are not necessarily limited, topolyaryletherketone (PEEK) and polyaryletherketoneketone (PEKK).Numerous advantages may be gained by constructing spacer 112 out ofmaterials such as PEEK and PEKK. The stiffness properties of PEEK andPEKK closely match that of bone. This reduces substantially thelikelihood that the spinous process will remodel around spacer 112causing a re-narrowing of the foraminal height and potentially resultingin revision surgeries. PEEK and PEKK are also substantially radiolucentwhich allows for improved post operative visualization of fusion betweenthe implant and the superior spinous process. Finally, by using the nonbone material with strategically placed apertures, fusion may beconfined to areas where it is useful. By way of example only, spacer 112may include fusion apertures only along the top (and potentiallyposterior side 113) such that fusion occurs only between the superiorspinous process and spacer 112. In this manner, extension is limitedwithout disadvantageously limiting flexion as well.

As depicted in FIG. 13, the main chamber 116 extends through the lateralsides 115 of the spacer 112. Main chamber 116 may be provided in any ofa variety of suitable shapes in addition to the generally cylindricalshape shown, including but not limited to a generally oblong,triangular, rectangular shape and/or combinations thereof. Main chamber116 may be dimensioned to receive fusion inducing materials 32, as bestillustrated in FIG. 14. Again, such fusion inducing materials mayinclude, but are not necessarily limited to BMP1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14 . . . n, demineralized bone matrix, allograftcancellous bone, autograft bone, hydroxy appetite, coral and/or otherhighly porous substance. The fusion inducing materials 32 may be packedinto main chamber 16 before and/or after fixing spacer 10 to the spinousprocess. The fusion inducing material 32 packed within main chamber 16may communicate openly with the superior spinous process through any ofthe insertion tool apertures 118 a, 118 b, 118 c, fusion apertures 124,and/or tether apertures 122. Through this communication, fusion mayoccur from the superior spinous process into the main chamber 116,permanently fixing spacer 112 in position.

With reference to FIGS. 15-19, the various features of spacer 112 willnow be described according to one preferred embodiment. FIG. 16 is aview of the top of spacer 112. Fusion notch 120 may be located generallyon the top surface towards the middle portion of the spacer 112. Fusionnotch 120 generally comprises a slot or indent dimensioned to receive aninferior portion of a superior spinous process. The notch 120 helpscenter the spacer 112 relative to the superior spinous process and mayassist in limiting side-to-side motion of spacer 112 prior to fusion.Fusion notch 120 includes main fusion aperture 124 a. Main fusionaperture 124 a extends into main chamber 116 and is the main avenue forfusion between main chamber 116 and the superior spinous process.Secondary fusion apertures 124 b may be located along the top of spacer112 near the four corners of fusion notch 120 and extend into mainchamber 116. Secondary fusion apertures 124 b may provide additionalroutes for fusion to the superior spinous process. Tether apertures 122may be located along the top center of spacer 112 near either side offusion notch 120. Tether apertures 122 are dimensioned to receivetethers 14, 15 to temporarily fix spacer 112 in position until fusion tothe superior spinous process occurs, permanently fixing spacer 112 inplace.

Main fusion aperture 124 a, secondary fusion apertures 124 b, and tetherapertures 122 may each be provided in any of a variety of shapes inaddition to the generally circular shapes shown, including but notnecessarily limited to, generally square, rectangular, oblong,triangular, and/or any combination thereof.

FIG. 16 illustrates the posterior side 113 of spacer 112. The posteriorside 113 may include 3 separate pairs of insertion tool apertures 118 a,118 b, and 118 c. As will be described in more detail below, havingthree pairs of insertion apertures allow different insertion approachesto be utilized without needing to make available separate tools and/orspacers with alternate aperture configurations. Insertion tool aperturesextend into main chamber 116 and may serve as additional fusion routesafter insertion, this may further solidify and strengthen the fusionbetween the superior spinous process and spacer 112.

FIG. 17 illustrates the anterior side 114 of spacer 112 and FIG. 18illustrates the bottom of the spacer. The anterior side 114 ispreferably free of any apertures (except, secondary fusion apertures 124b may be located near the top of spacer 112 on the anterior side). Whenpositioned in the inter spinous process space, the anterior side 114faces the spinal canal. Bone growth along the anterior side couldpotentially interfere with the spinal canal and the delicate neuraltissue located inside, which could result in pain and/or further surgeryfor the patient. The lack of communication to main chamber 116 caused bythe absence of apertures on the anterior side 114 advantageouslyprevents bone growth in the area. Likewise, the bottom of spacer 112 isalso aperture free and does not communicate with main chamber 116. Thisadvantageously prevents bone growth in the area and fusion to theinferior spinous process will not occur. Again, this allows the spinalsegment to maintain flexion ability while still correcting the stenosis.The bottom of spacer 112 may preferably have a concave surface such thatthe distance from top to bottom of spacer 112 is greater neareast thelateral sides 115 and lesser near the center. The concave bottom mayrest along the inferior spinous process and helps maintain spacer 112 ina centered position relative to the inferior spinous process. FIG. 19illustrates again a lateral side 115 with main chamber 116 extendingtherethrough.

To assist in visualization of spacer 112, both during and after surgery,spacer 112 may include at least one marker. Preferably, spacer 112includes a top marker 126 and two side marker 128. Markers 126, 128 maybe comprised of biocompatible radio-opaque material, such as for exampleonly, titanium (or other metals or polymers). Marker 126 may bepositioned along the center of spacer 112 within fusion notch 120.Preferably marker 126 extends through spacer 112 down to the bottomsurface. Markers 128 may be located in the lateral sides below mainchamber 116. During and after placement of the spacer 112, markers 128and 128 may be utilized to correctly orient spacer 112.

Utilizing X-ray fluoroscopy and/or other suitable imaging techniquesfrom the posterior (or the back of the patient) perspective of thespacer 112, the marker 126 situated in the center and extending fromfusion notch 120 to the bottom surface should make a line between thesuperior spinous process and the inferior spinous process viewable onthe fluoroscopy screen when the spacer 112 is properly positioned, aspictured in FIG. 30. Markers 128 should be positioned on each side ofthe superior and inferior spinous process in the inter spinous processspace. Drawing an imaginary line between markers 128 and connecting thatline to an imaginary line extending marker 126 to it should form anupside down “T” if properly positioned. From a lateral view, the depthof the spacer 112 in the interspinous space may be verified. Marker 126runs along the posterior side 113 of spacer 112. One or both of markers128 may be positioned in the lateral side 115 near the posterior side113. In one embodiment, one marker 128 is positioned near the posteriorside 113 and one marker 128 may be positioned near the anterior side114. On a lateral fluoroscopy view taken during surgery the position ofthe markers 126 and 128 may be viewed in relation to the posterior endof the spinous processes and the more anterior vertebral elements toensure spacer 112 is neither too far anteriorly nor to far posoteriorly.Drawing an imaginary line between markers 128 and connecting that lineto an imaginary line extending marker 126 to it should form an backwards“L” if properly positioned, as pictured in FIG. 31.

The spinal apparatus 10 of the present invention may be introduced intoa spinal target site through the use of any of a variety of suitableinstruments having the capability to releasably engage the spacer 12,112. In a preferred embodiment, the insertion tool permits quick,direct, accurate placement of the spacers 12, 112 between an upper andlower spinous process. An exemplary insertion tool is shown anddescribed in commonly owned U.S. Pat. No. 6,923,814 entitled “System andMethod for Cervical Fusion,” which is expressly incorporated byreference as if set forth fully herein. FIGS. 21-23 depict an exemplaryinsertion tool 200 for use with spacers 12, 112. At a distal end 202,insertion tool 200 includes a pair of prongs 204 dimensioned to engageinsertion apertures 18 and 118 a, 118 b, 118 c such that spacer 12, 112becomes temporarily attached to the distal end 202 for insertion. Aspictured in FIG. 24 insertion apertures 118 a are aligned laterally inthe center of spacer 112 such that spacer 112 and insertion tool 200mate at approximately the center point of the spacer. This configurationmay be advantageous if approaching the inter spinous process space froma directly posterior approach. As pictured in FIG. 23, insertionapertures 118 b (and 118 c) are aligned vertically near the side ofspacer 112. This configuration may be advantageous if approaching from amore lateral direction.

In order to use the spinal apparatus 10 of the present invention in atreatment of spinal stenosis, a clinician must first designate theappropriate spacer size 12, 112. A clinician can utilize the spinalapparatus 10 in either an open or minimally invasive spinal fusionprocedure. In either type of procedure, a working channel would becreated in a patient that reaches a targeted spinal level. After thecreation of the working channel, the interspinous space would beprepared. After preparation a sizer instrument is used to determine theappropriate size of the spacer 12, 112. One exemplary sizer instrument300 is illustrated by way of example only in FIGS. 24-27. Sizerinstrument 300 includes a handle portion 302 and an implant portion 304.Handle portion 302 may be configured in any variety of suitable shapesand sizes. Implant portion 304 may be provided in a variety of sizesmatching the various sizes of spacer 112. As pictured, sizer implant maybe proved in an asymmetrical shape where the side opposite the handle302 has a lesser height than the side to which handle 302 is attached.This may allow the implant portion 304 to be rotated into position withminimal interference from the spinous process. Although it is not shown,it is conceived that spacer 112 may also be provided in thisasymmetrical fashion.

Preparation of the inter spinous process space includes perforating theinterspinous ligament between the superior and inferior spinousprocesses. The supraspinous ligament may preferably be left intact anddistracted out of the way if necessary. A key part of the preparationincludes abrading the inferior portion of the superior spinous processwhere it will communicate with the fusion inducing materials 32 packedin the main chamber 16, 116. Abrading removes the hard cortical bonefrom the inferior surface of the superior spinous process and leavesbleeding bone which is better adapted for fusion. As new bone generatesto heal the abraded portion it may grow into the main chamber 16, 116,fixing spacer 12, 112 to the superior spinous process.

In one embodiment described above the spacer 12, 112 is held in positionwith tethers 14, 15 attached to the spinous process through tether lumen22, 122. According to an alternate embodiment, pictured by way ofexample only in FIGS. 30-31 an alternate securing mechanism may be usedto fix spacer 12, 112 in place. The alternate securing mechanismincludes a zip cable 400 and a pair of locking bases 402 404. Base 402may be integral with cable 400. Base 402 is positioned on the top ofspacer 12, 112 next to the fusion notch 20, 120 and fixed to the spacer12, 112 via tether apertures 22, 122. Base 402 is positioned over tetheraperture 22, 122 and a locking pin 406 is inserted through the base intotether aperture 22, 122. The step is repeated for base 404 on theopposite side of the fusion notch 20, 120. Once both bases are inposition and the spacer 12, 112 is positioned between the spinousprocesses, the zip cable 400 may be wrapped around the superior spinousprocess and fed through the opposing base 404. Teeth 408 on the cable400 prevent cable 400 from loosening and thus holds the spacer 12, 122in place for fusion to occur. Any of a variety of suitable materials maybe used to form the zip cable 400, bases 402, 404, and locking pins 406.In one exemplary embodiment the cable 400 and bases 402, 404 arecomprised of nylon and the locking pins 406 are comprised of titanium.

When the spacer 12, 112 is positioned and inserted into the preparedspace between the spinous processes it forces the spinous processesapart. The spine flexes as the spinous processes are forced apart andthe neuroforamina and the spinal canal are enlarged as the spine isflexed. The spinal apparatus 10 holds the vertebrae in a flexedposition, preventing extension but advantageously allowing flexion.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined herein.

1-22. (canceled)
 23. A system for treating spinal stenosis, comprisingan implant, the implant dimensioned to fit between a superior spinousprocess and an inferior spinous process, the implant being configured topromote fusion to the superior spinous process, the implant furtherbeing configured to discourage fusion to the inferior spinous process;and at least one of a tether, screw, clamp, and zip cable to couple theimplant to the superior spinous process.
 24. The system of claim 0,wherein the implant includes at least one aperture to allow bone to growinto the implant.
 25. The system of claim 0, wherein the implantincludes an interior chamber in communication with the at least oneaperture, the chamber dimensioned to receive fusion inducing materialone of before and after coupling the implant to the spinous process. 26.The system of claim 0, wherein the fusion inducing material includes anyof Bone Morphogenic Protein, demineralized bone matrix, allograftcancellous bone, autograft bone, hydroxy appetite, and coral.
 27. Thesystem of claim 0, wherein the at least one aperture is positioned suchthat it contacts the superior spinous process.
 28. The system of claim 0of, wherein the implant includes an aperture for releasably attaching aninsertion tool.
 29. The system of claim 28, wherein the insertion toolincludes a pair of prongs that engage a pair of insertion aperturesdimensioned to receive the prongs.
 30. The system of claim 29, whereinthe implant includes at least two pairs of apertures for engaging theinsertion tool in different orientations.
 31. The system of claim 0,wherein the tether is one of a wire, cable, suture, and allografttissue.
 32. The method of claim Error! Reference source not found.,wherein the implant includes at least one aperture dimension to receivethe tether and comprising the additional step of tying the tether eachof through the at least one aperture dimensioned to receive the tetherand the superior spinous process.
 33. The system of claim 0, wherein azip cable is used, the zip cable including a cable, two bases and twolocking pins, the cable being dimension to wrap around the superiorspinous process and lockingly engage both bases.
 34. The system of claim0, wherein the implant includes a main aperture to allow bone growthinto the implant and at least one secondary aperture to allow bonegrowth into the implant.
 35. The system of claim 0, wherein the implantincludes a notch dimensioned to receive a portion of the superiorspinous process.
 36. The system of claim 35, wherein the at least oneaperture for allowing bone to grow into the implant is positioned withinthe notch.
 37. The system of claim 36, wherein a second notch ispositioned on a bottom of the implant and is dimensioned to engage theinferior spinous process.
 38. The system of claim 0, wherein the implantis made of non-bone material.
 39. The system of claim 38, wherein theimplant is made from one of polyetheretherketone andpolyetherketoneketone.
 40. The system of claim 38, wherein the implantincludes at least one radio-opaque marker viewable using an imagingtechnique.
 41. The system of claim 40, wherein the marker is positionedat the center of the implant in a posterior-anterior direction, themarker being alignable with a top portion of the superior spinousprocess and inferior spinous process to ensure proper placement.
 42. Thesystem of claim 41, wherein additional markers are positioned in sidesof the implant, at least one side marker being positioned in anterioraspect of the implant, the side marker in the anterior aspect of theimplant being alignable relative to the spinal canal.
 43. (canceled)